Finish merging lecture

merging/merging.tex

@@ -168,167 +168,89 @@ $ git log --oneline --decorate --graph --all
 
 \begin{frame}
   \frametitle{Remote branches}
-  In this course, we don't really use branches, except:
+  In this course, we don't really discuss branches, except:
   \begin{itemize}
     \item Commits from a remote show up as a remote branch.
     \item Even with only a \bt{master} branch, remotes might still diverge.
     \item Merging remote branches is just like merging local branches.
   \end{itemize}
   \bigskip
-  \includegraphics[width=10cm]{images/example-hue-ahead}
+  \includegraphics[width=10cm]{images/example-hue}
 \end{frame}
 
 
-\section{Manipulating the commit graph}
+\section{Merging from remotes}
 
 \begin{frame}
   \frametitle{An example repository}
-  \includegraphics[width=8cm]{images/example}
+  \includegraphics[width=10cm]{images/example-hue}\\
+  \bigskip
+  Branch \bt{master} on \bt{hue} is one commit ahead of our \bt{master} and we
+  have already seen how to merge \bt{hue/master} into \bt{master}:
   \begin{itemize}
-    \item Branches \bt{license} and \bt{interface} diverged from \bt{master}.
-    \item Only \bt{license} has been merged back into \bt{master}.
-    \item Current branch is \bt{master}.
+    \item \bt{git merge hue/master}
+    \item This was easy: Git just moves \bt{master} (and \bt{HEAD}) to point
+      to \bt{hue/master}.
+    \item It is called a {\em fast forward merge}.
   \end{itemize}
 \end{frame}
 
 \begin{frame}[fragile]
-  \frametitle{Creating a new branch: \bt{git branch}}
-  \begin{lstlisting}
-$ git branch lib
-  \end{lstlisting}
-  \bigskip
-  Creates branch \bt{lib} at \bt{HEAD}.
-  \pause
-  \bigskip
-  \begin{lstlisting}
-$ git checkout lib
-Switched to branch 'lib'
-  \end{lstlisting}
-  \pause
-  \bigskip
-  Or, for Git pro's, in one command:
+  \frametitle{Fast forward merging: \bt{git merge}}
+  If a remote branch is ahead of us, it can be merged easily:
   \bigskip
   \begin{lstlisting}
-$ git checkout -b lib
-Switched to a new branch 'lib'
+$ git merge hue/master
+Updating c7f3bd9..251a51b
+Fast-forward
+testlib.py |    2 +
+1 file changed, 2 insertions(+)
   \end{lstlisting}
   \bigskip
-  At this point, \bt{lib} is just a label to the same commit as \bt{master}.
+  \includegraphics[width=10cm]{images/example-hue-merged}
 \end{frame}
 
-\begin{frame}
-  \frametitle{Our example repository}
-  \includegraphics[width=8cm]{images/example-branched}\\
-  \vspace{0.5cm}
-  Created branch \bt{lib} from \bt{master}.
-\end{frame}
-
-\begin{frame}[fragile]
-  \frametitle{Working on a branch: \bt{git commit}}
-  We can extend the \bt{lib} branch by adding commits.
-  \bigskip
-  \begin{lstlisting}
-$ echo 'VERSION=1' > testlib.py
-$ git add testlib.py
-$ git commit -m 'Add empty testlib'
-  \end{lstlisting}
-  \pause
-  \bigskip
-  \begin{lstlisting}
-$ git log --oneline --decorate --graph --all
-* 251a51b (HEAD, lib) Add empty testlib
-* c7f3bd9 (master) Add .gitignore file
-| * 8fc25c1 (interface) Trivial Python interface
-|/
-*   4a44c4e Merge branch 'license'
-|\
-| * 0fbe3e3 (license) Add MIT license
-...
-  \end{lstlisting}
-\end{frame}
 
 \begin{frame}
-  \frametitle{Our example repository}
-  \includegraphics[width=8cm]{images/example-committed}\\
-  \vspace{0.5cm}
-  Extended branch \bt{lib}.
-\end{frame}
-
-\begin{frame}[fragile]
-  \frametitle{Fast forward merging: \bt{git merge}}
-  Let's merge our work on \bt{lib} back into \bt{master}.
-  \bigskip
-  \begin{lstlisting}
-$ git checkout master
-Switched to branch 'master'
-$ git merge lib
-Updating c7f3bd9..251a51b
-Fast-forward
- testlib.py |    1 +
- 1 file changed, 1 insertion(+)
- create mode 100644 testlib.py
-  \end{lstlisting}
+  \frametitle{An example repository}
+  \includegraphics[width=8cm]{images/example-hue-diverged}\\
   \bigskip
-  This merge was easy:
+  Branch \bt{master} on \bt{hue} and our \bt{master} have diverged and merging
+  now seems less straightforward.
   \begin{itemize}
-    \item \bt{lib} was directly upstream of \bt{master}.
-    \item Git just moves \bt{HEAD} and \bt{master} to point to \bt{lib}.
-    \item This is called a {\em fast forward merge}.
+    \item \bt{git merge hue/master}
+    \item Git will create a new commit in which it combines both changes.
+    \item It is called a {\em three-way merge}.
+    \item The {\em merge commit} has two parents.
   \end{itemize}
 \end{frame}
 
-\begin{frame}
-  \frametitle{Our example repository}
-  \includegraphics[width=8cm]{images/example-merged-ff}\\
-  \vspace{0.5cm}
-  Merged branch \bt{lib} into \bt{master} (fast forward).
-\end{frame}
-
 \begin{frame}[fragile]
   \frametitle{Three-way merging: \bt{git merge}}
-  Let's merge our work on \bt{interface} back into \bt{master}.
+  Let's merge the remote work on \bt{master} back into our local \bt{master}:
   \bigskip
   \begin{lstlisting}
-$ git merge interface
+$ git merge hue/master
 Merge made by the 'recursive' strategy.
- interface.py |    3 +++
- 1 file changed, 3 insertions(+)
- create mode 100755 interface.py
+ FACTS.md | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
   \end{lstlisting}
   \bigskip
-  This merge was harder:
-  \begin{itemize}
-    \item \bt{interface} and \bt{master} had diverged.
-    \item Git determines changes in \bt{interface} and \bt{master} since their
-      most recent common ancestor and creates a new commit from that.
-    \item This is called a {\em recursive three-way merge} and the resulting
-      merge a {\em merge commit}.
-  \end{itemize}
-\end{frame}
-
-\begin{frame}
-  \frametitle{Our example repository}
-  \includegraphics[width=8cm]{images/example-merged}\\
-  \vspace{0.5cm}
-  Merged branch \bt{interface} into \bt{master}.
+  \includegraphics[width=9cm]{images/example-hue-merged2}
 \end{frame}
 
 \begin{frame}[fragile]
-  \frametitle{Deleting branches: \bt{git branch}}
-  Old branches that have been merged can be deleted.
-  \bigskip
-  \begin{lstlisting}
-$ git branch -d interface
-Deleted branch interface (was 8fc25c1).
-  \end{lstlisting}
+  \frametitle{The other way around}
+  \bt{git push} also does an implicit \bt{git merge} on the remote.
+  \begin{itemize}
+    \item We send our local commits to the remote.
+    \item They are merged into the remote branch.
+    \item But only if this is a fast-forward merge.
+    \item Diverging commits {\em cannot be pushed directly}.
+  \end{itemize}
   \bigskip
-  \begin{lstlisting}
-$ git branch -d lib license
-Deleted branch lib (was 251a51b).
-Deleted branch license (was 0fbe3e3).
-  \end{lstlisting}
   \bigskip
-  No history is lost, just labels removed.
+  \includegraphics[width=10cm]{images/example-hue-pushed}
 \end{frame}
 
 
@@ -355,14 +277,13 @@ Deleted branch license (was 0fbe3e3).
 \begin{frame}[fragile]
   \frametitle{Setting the stage (1/3)}
   \begin{lstlisting}
-$ git log --oneline --decorate --graph --all
-* 9d2ad27 (HEAD, master) State character preference
-| * 374ab60 (simpsons) State character preference
+* 5edaf08 (hue/master, hue/HEAD) State character preference
+| * f1ef19c (HEAD, master) State character preference
 |/
-* 4012f4f Initial commit
+* 1f6d2ab Initial commit
   \end{lstlisting}
   \bigskip
-  We'd like to merge branch \bt{simpsons} into \bt{master}.
+  We'd like to merge branch \bt{hue/master} into \bt{master}.
 \end{frame}
 
 \begin{frame}[fragile]
@@ -370,15 +291,14 @@ $ git log --oneline --decorate --graph --all
   The last commit on \bt{master}:
   \bigskip
   \begin{lstlisting}
-$ git show --oneline
-9d2ad27 State character preference
-diff --git a/README b/README
+f1ef19c State character preference
+diff --git a/FACTS.md b/FACTS.md
 index de15194..ef40359 100644
---- a/README
-+++ b/README
+--- a/FACTS.md
++++ b/FACTS.md
 @@ -1,2 +1,4 @@
- Facts about television series
- =============================
+Facts about television series
+=============================
 +
 +My favorite character is Eric Cartman.
   \end{lstlisting}
@@ -386,29 +306,29 @@ index de15194..ef40359 100644
 
 \begin{frame}[fragile]
   \frametitle{Setting the stage (3/3)}
-  The last commit on \bt{simpsons}:
+  The last commit on \bt{hue/master}:
   \bigskip
   \begin{lstlisting}
-$ git show --oneline simpsons
-374ab60 State character preference
-diff --git a/README b/README
-index de15194..9dd729b 100644
---- a/README
-+++ b/README
+$ git show --oneline hue/master
+5edaf08 State character preference
+diff --git a/FACTS.md b/FACTS.md
+index de15194..5e69508 100644
+--- a/FACTS.md
++++ b/FACTS.md
 @@ -1,2 +1,4 @@
- Facts about television series
- =============================
+Facts about television series
+=============================
 +
-+My favorite character is Homer Simpson.
++My favorite character is Milhouse.
   \end{lstlisting}
 \end{frame}
 
 \begin{frame}[fragile]
   \frametitle{Creating a merge conflict}
   \begin{lstlisting}
-$ git merge simpsons
-Auto-merging README
-CONFLICT (content): Merge conflict in README
+$ git merge hue/master
+Auto-merging FACTS.md
+CONFLICT (content): Merge conflict in FACTS.md
 Automatic merge failed; fix conflicts and then
 commit the result.
   \end{lstlisting}
@@ -420,7 +340,7 @@ $ git status
 #   (use "git add/rm <file>.." as appropriate to
 #    mark resolution)
 #
-#              both modified:      README
+#              both modified:      FACTS.md
 #
 no changes added to commit (use "git add" and/or
 "git commit -a")
@@ -430,23 +350,23 @@ no changes added to commit (use "git add" and/or
 \begin{frame}[fragile]
   \frametitle{Resolving a merge conflict (1/2)}
   \begin{lstlisting}
-$ cat README
+$ cat FACTS.md
 Facts about television series
 =============================
 
 <<<<<<< HEAD
 My favorite character is Eric Cartman.
 =======
-My favorite character is Homer Simpson.
->>>>>>> simpsons
+My favorite character is Milhouse.
+>>>>>>> hue/master
   \end{lstlisting}
   \bigskip
-  What we had is under \bt{HEAD}, what \bt{simpsons} had is above
-  \bt{simpsons}.
+  What we had is under \bt{HEAD}, what \bt{hue/master} had is above
+  \bt{hue/maser}.
   \pause
   \bigskip
   \begin{lstlisting}
-$ emacs README
+$ nano FACTS.md
   \end{lstlisting}
 \end{frame}
 
@@ -455,21 +375,21 @@ $ emacs README
   We resolve the conflict by hand.
   \bigskip
   \begin{lstlisting}
-$ cat README
+$ cat FACTS.md
 Facts about television series
 =============================
 
 My favorite characters are Eric Cartman
-and Homer Simpson.
+and Milhouse.
   \end{lstlisting}
   \pause
   \bigskip
   And can now finish the merge commit.
   \bigskip
   \begin{lstlisting}
-$ git add README
+$ git add FACTS.md
 $ git commit
-[master 1e496cb] Merge branch 'simpsons'
+[master 1e496cb] Merge remote-tracking branch 'hue/master'
   \end{lstlisting}
 \end{frame}
 
@@ -479,9 +399,9 @@ $ git commit
   \bt{git merge --abort}.
   \bigskip
   \begin{lstlisting}
-$ git merge simpsons
-Auto-merging README
-CONFLICT (content): Merge conflict in README
+$ git merge hue/master
+Auto-merging FACTS.md
+CONFLICT (content): Merge conflict in FACTS.md
 Automatic merge failed; fix conflicts and then
 commit the result.
   \end{lstlisting}
@@ -505,9 +425,9 @@ nothing to commit (working directory clean)
 $ git mergetool
 merge tool candidates: meld opendiff kdiff3 ...
 Merging:
-README
+FACTS.md
 
-Normal merge conflict for 'README':
+Normal merge conflict for 'FACTS.md':
   {local}: modified file
   {remote}: modified file
 Hit return to start merge resolution tool (meld):